1. Field of the Invention
The present invention relates to encoding and decoding fields, and more particularly to an encoding apparatus and method, and a decoding apparatus and method, for performing signal detection and/or error correction by interconnecting only soft-type encoding apparatuses.
2. Description of the Related Art
Generally, signals transmitted through various transmission channels, for example, a spatial medium for digital television broadcasting or a recording medium, such a CD, a DVD, etc., have certain signal distortion. In order to restore the distorted signals, various signal detection and error correction techniques have been developed.
Conventional data detection and error correction techniques include hard encoding/decoding methods such as a Reed Solomon code, a BCH code, etc., and soft encoding/decoding methods such as a Turbo code, Low Density Parity Check (LDPC) code, etc.
A decoder that implements the hard decoding methods receives a data word including a hard value of “1” or “−1” from a demodulator, and outputs an error-corrected data word. Further, the decoder that implements the soft decoding methods receives a soft value representing probability of the data word from the demodulator, and outputs the error-corrected data word. That is, the input of the soft decoder is not a hard value of “1” or “−1” but a soft value such as “0.8”, “−0.8”, etc., where the soft value itself includes probability of a data word value being “1” or “−1”.
Meanwhile, both the decoder implementing the hard encoding methods and the decoder implementing the soft encoding methods have a function of adding parity information to transmission data, in order to perform the operations described above.
Such conventional techniques, which perform the data detection and the error correction using hard coding and soft coding, include a method which uses only either the hard coding or the soft coding, a method which performs successive encoding/decoding by using the hard coding and the soft coding together, a method which decodes by repeating the hard coding, and a method which uses the hard coding and the soft coding together but merely adds a hard-type output as additional information to a soft-type output, etc.
However, all of the above conventional techniques have difficulties in obtaining a satisfying performance in detection and error correction performance. Specially, the conventional techniques, which merely connect the hard coding and the soft coding has a problem in that information loss occurs in a process of converting the output information of the soft-type decoder into the information suitable for the hard-type decoder, and complexity increases significantly in a case of decoding the output information into the soft-type data.